[all-commits] [llvm/llvm-project] 665060: [BasicAA] Remove misleading overflow check

[Nikita Popov via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 665060ea4583fa1773a900d81b71c489aaf3e8e4
      https://github.com/llvm/llvm-project/commit/665060ea4583fa1773a900d81b71c489aaf3e8e4
  Author: Nikita Popov <nikita.ppv at gmail.com>
  Date:   2021-10-27 (Wed, 27 Oct 2021)

  Changed paths:
    M llvm/lib/Analysis/BasicAliasAnalysis.cpp

  Log Message:
  -----------
  [BasicAA] Remove misleading overflow check

GEP decomposition currently checks whether the multiplication of
the linear expression offset and GEP scale overflows. However, if
everything else works correctly, this overflow check is both
unnecessary and dangerously misleading. While it will avoid an
overflow in Scale * Offset in particular, other parts of the
calculation (including those on dynamic values) may still overflow.
The code working on the decomposed GEPs is responsible for ensuring
that it remains correct in the presence of overflow. D112611 fixes
the last issue of that kind that I'm aware of (in fact, the overflow
check was originally introduced to work around precisely that issue).

Differential Revision: https://reviews.llvm.org/D112618